Refillable electric fuse



Jan. 23, 1923. 1,443,137. F. C. LA MAR.

REFILLABLE ELECTRIC FUSE. ORIGINAL FILED JUNE 3. .1920.

INVENTOR. 5'

ATToR/I/Ey.

Patented Jan. 23,. 1923.

UNITED'l STATES PATENT oFFicE.

FRANK C. LA MAR, OF PITTSBURGH, PENNSYLVANIA.

BEFILLABLE ELECTRIC FUSE.

Application filed .Tune 3, 1920, Serial No. 386,280. Renewed August 4, 1922. Serial No. 579,771.

To all whom t may concern.'

Be it known that I, FRANK C. LA MAR, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a certain new and useful Improvement in Refillable Electric Fuses, of which the following is a specification.

This invention ielates to refillable electric fuses. I

The object of the invention is to provide a refillable electric fuse of simple and economical construction, and to produce a fuse of this sort so constructed and assembled that it will be absolutely impossible to load or refill the fuse above its normal rated or predetermined capacity, and thereby cause injury to motors and other electrical apparatus or installations in which the fuses are the protecting elements, and which often occurs when the fuses are reloaded by unskilled or maliciously careless attendants.

So far as I am aware I am the first to Iproduce a refillable fuse of this sort which will absolutely protect such a fuse against being overloaded and causing the damaging effects just mentioned.

In all other fuses of the refillable and other types, so far as I am aware, it has been easily possible to load the fuse with other elements or parts far in excess to their rated or predetermined capacities, and which overloading of fuses of this sort now in general use considerable damage has occurred to the machinery operated by the circuit in which the fuses are the protecting ele-ments, and thereby causing considerable delay and interruption'of service from such circuit or cir-l cuits. and it isv the object and purpose of this invention to avoid such objections and difiiculties which frequently-result with the fuses now in use, by improper and sometimes malicious overloading.

The invention consists in a refillable fuse, comprising a easing, a fuse element permanently fixed in said casing, fuse elements adapted to be removably fitted in the ends of the casing and contacting with the tei'- niinals of the fixed fuse element, and means for holding said last named fuse elements in place.

The invention also consists in a refillable fuse comprising a casing, a plug permanently fitted in the casing and carrying a fuse `element. fixed therein and having its terminals exposed at the opposite ends of the plug, removable plugs adapted to be fitted in the ends of the casing, and fuse elements adapted to be engaged or carried by the said end plugs, and end caps tted upon the ends of the casing adapted to engage the fuse elements and end plugs to force them in place and hold the fuse elements carried thereby into engagement with the exposed terminals of the permanent fuse element. l

The invention also consists in thedetails of construction and combination of parts, all substantially, as I will proceed now more particularly to set forth and finally claim.

In the accompanying drawings, illustrating the invention, in the several views of which like parts are 'similarly designated, Figure 1 is a longitudinal section. Fig. 2 is a transverse section on the line 2-2,fFig. l. Fig. 3 is a perspective view of the fuse with the parts disassembled, one of the end caps being omitted. Fig. 4 is a side view of the main or permanent fuse element and its sup porting or anchoring plug detached, and Fig. 5 is an end View thereof.

In the drawings, l is the casing, which may be constructed of any suitable insulating or refractory substance. The ends of the casing are provided with the usual screwthreads, which may be formed directly upon the material of the casing, but herein shown as metallic screwthreaded thimbles 2 fitted upon the ends of the casing. l

Permanently fixed Within the casing l is the main portion of a fuse element 3, and as shown in the drawings, this fuse element is secured to a plug 4 of suitable insulating or refractory material. The plug 4 is preferably circular in cross-section, to fit snugly within the casing 1, and is somwhat shorter than the casing so its ends Will reach a suit able distance from the ends of the casing when placed in the casing. The opposite ends of the plug are beveled in the same diout and the strip bent down into the grooves 7 upon the opposite sides of the plug, and the fiattened ends 8 bent down and over the projecting ends' of the plug to form good contact surfaces, as shown in lFig. 5.

llhe fuse element and its supporting and anchoring plug as thus assembled is fitted about centrally into the casing and cemented or otherwise permanently fixed in place with its terminal contact ends exposed at opposite ends, and adapted to be engaged by removable fuse elements adapted to be fitted in the ends of the casing.

As herein shown the removable fuse elements 9 are constructed of short pieces of suitable fusible metal, and comprises a substantially circular head 10 and a crescent shaped head 11 connected by a narrow neck portion 12 adapted to be fitted upon substantially circular shaped supporting and anchoring blocks 13 of suitable yinsulating or refractory material, the head 10 of the fuse element engaging theouter flat end 14 of the blocks, the neck 12 bent down upon a flat slabbed-off portion 15 of the block and slightlybulged over inclined portion 16 of the inner end of the block and the head 11 of the fuse element bent inwardly and under against an outwardly inclined' portion 17 of the block. As thus assembled, the blocks and fuse elements may be inserted in the ends of the casing, and the metal screw-threaded end caps 18 fitted upon the threaded ends of the casing and screwed to place, whereby the inner walls of the end caps engage the heads 10 ot' the fuse elements and torce the blocks into the casing and the inner heads 11 into forcible and good contact with the flattened terminals of the permanently fixed fuse element 3.

ln order to properly position and prevent the blocks 13 from turning in the casing, the casing may be provided with grooves 1 and the blocks 13 with longitudinal ribs 13 to engage said grooves when the parts are assembled.

The blocks 13 are made to fit loosely in' the ends4 of the casing, so they will readily drop out or the casing when disassembling the fuse for reloading.

As thus assembled, and as shown in Fig. 1, it will be observed that the abutting beveled ends-ot` the plug 4 and the blocks 13 afford spaces 19 for the bulged portions of the removable fuse elements and constitute gas chambers for the gas due to the fusing of the fuse elements at this point in case of a blow out, the end caps beingprovided with the usual gas escape openings 20.

ln constructing the fuse and to carry out the purpose of this invention, the main and permanently fixed portion of the fuse element 3 is prepared to have a certain rated or predetermined capacity and the short ments in place of those which have been blown.

Should the fuse, by mistake or otherwise, be reloaded with fuse elements of a greater capacity than the main or permanently fixed fuse element, and the fuse be subjected to a current in excess of the` capacity of the main fuse element, then the main fuse ele- Sil ment will blow out and rupture the circuit and thus avoid damage and burning out of the machinery or other apparatus operated thereby, which would otherwise have occurred due to the overloading of' the fuse.

lin case of a blow out under normal conditions or otherwise, the gas created by the melting of the fuse elements will fill the gas chambers 19 and find its way to the rear or outer ends of the blocks 13 and force the blocks inwardly against the ends of the fixed plug 4 and thereby automatically'seal the gap between the terminals of the fixed fuse element and the end caps or between the short fuse elements, as the case may be.

So also in case of a blow out due to overloading with removable fuses in excess of the capacity of the main or fixed fuse element, the main or fixed fuse element will be destroyed and permanently opening a gap in the circuit, and absolutely destroy the fuse so that it will be impossible to again reload the fuse for future use.

l have herein shown the casing provided with ordinary end caps, such as commonly used in the ferrule type of fuse, but it will be understood that the end caps may be provided with knife blades to constitute the well known knife blade ltype of fuse.

l wish to be understood that I do not limit the invention to the specific details of construction and arrangement of parts herein shown and described, as the same may be altered in various particulars and still be within the scope of the appended claims.

1. A refillable electric fuse, comprising a casing, a main fuse element fixed in said casing beyond the opposite ends thereof, and removable fuse elements adapted to be fitted in the ends of the casing and contacting with the opposite ends of the main fuse element.

2. A refillable electric fuse, comprising a casing, a main fuse element permanently fixed in said casing beyond the opposite ends thereof, and removable fuse elements adapted to be fitted in the ends of the casingy and contacting With the opposite ends of the main fuse element.

3. A refillable electric fuse, comprising a casing, a main fuse element of a certain capacity fixed in said casing beyond the opposite ends thereof, and removable fuse elements 'of less capacity than the main fuse element adapted to be fitted in the ends of the casing and contacting With the opposite terminals of the main fuse element.

4. A refillable electric fuse, comprising a casing, a main fuse element fixed in said casing beyond the op-posite ends thereof, removable fuse elements adapted to be fitted in the ends of the casing and contacting with the oppositeterminals of the main fuse element, and end caps fitted upon the casing for holding the removable fuses in place.

5. A refillable electric fuse, comprising a casing a plug fitted in said casing beyond .the opposite ends thereof, a .main fuse element fixed to said plug and having its terminals exposed at the opposite ends thereof Within the ends of the casing, and removable fuse strips adapted to be fitted in the ends of the casing and contacting with the terminals of the main fuse element, and means for holding said removable fuse elements in place. y

6, A refillable electric fuse, comprising a casing, a plug fitted in said casing, a main fuse element fixed to said plug and having its terminals exposed at the opposite ends thereof, removable blocks adapted to be fitted in the ends of the casing, removable fuse elements fitted to said blocks and adapted to be fitted in the ends of the casing with said blocks and contacting With the terminals of the main fuse element, and means for holding said removable blocks and fuse elements in place.

7. A refillable electric fuse, comprising a casing, a plug fitted in said casing and a main fuse element fiXed thereto and having its terminals exposed at the opposite ends of the plug, said plug and fuse element being permanently and immovably fixed in said casing, removable blocks adapted to be fitted in theI ends of the casing, removable fuse elements fitted to said blocks and adapted to be inserted in the ends of the casing with said blocks and contacting with the terminals of the main fuse element, and end caps adapted to be fitted upon the ends of the casing and contacting With the removable fuse elements and forcing and holding said removable blocks and their attached fuse elements in place.

In testimony whereof I hereunto set my hand this 3rd day of June 1920.

FRANK C'. LA MAR. 

